Checks for sh-only syntax

We aim for all our shell-scripts to be POSIX compliant. This means that
they should be written with sh-syntax only. In RedHat, the platform on which we
develop, sh is a link to bash, and bash is not very good at enforcing POSIX
compliance. The problem is that some Unix-like platforms do not install bash by
default, and even if they do, they have sh implementations that are very strict
at being POSIX compliant (e.g., dash in Debian, and /bin/sh in FreeBSD).

RedHat installs by default a script:
/usr/bin/checkbashisms,
that you can use to check for bash-only syntax in a sh script. If it is not
installed, it is part of the devscripts tarball from Debian. Here is an example run: